Apply a reduction function on the incoming elements and pass the result to the next invocation.
Apply a reduction function on the incoming elements and pass the result to the next invocation. The first invocation receives the two first elements of the flow.
Materializes into a
CompletionStage that will be completed by the last result of the reduction function.
val source = Source(1 to 10) val result = source.runWith(Sink.reduce[Int]((a, b) => a + b)) result.map(println)(system.dispatcher) // will print // 55
Source<Integer, NotUsed> ints = Source.from(Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)); CompletionStage<Integer> sum = ints.runWith(Sink.reduce((a, b) -> a + b), system); sum.thenAccept(System.out::println); // 55
backpressures when the previous reduction function invocation has not yet completed